From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 3FB7DD35157 for ; Wed, 1 Apr 2026 08:17:36 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id A741D6B0089; Wed, 1 Apr 2026 04:17:35 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A255D6B008A; Wed, 1 Apr 2026 04:17:35 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 93ADF6B0092; Wed, 1 Apr 2026 04:17:35 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 815C56B0089 for ; Wed, 1 Apr 2026 04:17:35 -0400 (EDT) Received: from smtpin10.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 2CE8CC6968 for ; Wed, 1 Apr 2026 08:17:35 +0000 (UTC) X-FDA: 84609282870.10.4235176 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf05.hostedemail.com (Postfix) with ESMTP id A9236100002 for ; Wed, 1 Apr 2026 08:17:33 +0000 (UTC) Authentication-Results: imf05.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b="Xouf/Qy7"; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf05.hostedemail.com: domain of ljs@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=ljs@kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1775031453; a=rsa-sha256; cv=none; b=77RocR9TAWm02b9Tzg3oHdmo5XFy3019lkG0V9T/OaWTmnkg0x/ZpIj6JbwQq2KC1RsDo6 fPUh+u3gCBz0skj+8YRDabYwpjY01uJJMtNnVUPogq9v7ih3GRawBQc1lnEQv+Au2elxhW QLYxGR49A1kasJHq3vAWjd0hrX6FDT4= ARC-Authentication-Results: i=1; imf05.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b="Xouf/Qy7"; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf05.hostedemail.com: domain of ljs@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=ljs@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1775031453; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=uiCKNu+0fsGWEP+vtJDcyL0C+4drAeM5niFdrnj+lMw=; b=VripL9wpYQvKDeuC8jMVmFAJ4u/ktULJTtnNGH6Q7Cez/Ymg/Mu4KVWQ83WEiTUbjQTwby WqVKqelVU3YoLcCjLAf4rjUO2AtyhWamzelMj6Xlv6fRiXcQkG7Woza4u7/rlmejkJ0mlS tSZn9az94U8Ch1/FrRuHsLzhkrBDu8w= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 10EDA600C4; Wed, 1 Apr 2026 08:17:33 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id F3A0AC2BC9E; Wed, 1 Apr 2026 08:17:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1775031452; bh=ZrZ0N0xKXR6C9RhW5WxZulhizSQSbcnecFJKI8W6SqA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Xouf/Qy72TBTDz2ReUXOIudIpg4FJ4N8n8mFM2mqYRs3SQw/ELMh9ZlQVKLNf4s4j AtAPP2k+6PIg0Q8am5+9adyIJ1+zPp8kmA9LyYhBrsVXpt9UgTYH+QugQj1Tze+e4N Vw6PPxeo/FWNcHZZOvcfxkIBsPqFPgFDt3eRfzEqiLn089UHbv+0NRnbyuFGf3JX+9 zNP0JbF54xE/8tbrlhV4yqik/5V8czyZ0uzQ7kgjUEAxVgNF35MldUQqKTDXzhyWo7 qC5NOzvPaAtralcqjwL/eLq2Zxw0kOfXxeY4ggzngtCJweDzk+I86o2FoE6JHG5oxF vZFBY7PHgt7mQ== Date: Wed, 1 Apr 2026 09:17:19 +0100 From: "Lorenzo Stoakes (Oracle)" To: "David Hildenbrand (Arm)" Cc: Nico Pache , Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org, aarcange@redhat.com, anshuman.khandual@arm.com, apopple@nvidia.com, baohua@kernel.org, baolin.wang@linux.alibaba.com, byungchul@sk.com, catalin.marinas@arm.com, cl@gentwo.org, corbet@lwn.net, dave.hansen@linux.intel.com, dev.jain@arm.com, gourry@gourry.net, hannes@cmpxchg.org, hughd@google.com, jackmanb@google.com, jack@suse.cz, jannh@google.com, jglisse@google.com, joshua.hahnjy@gmail.com, kas@kernel.org, lance.yang@linux.dev, Liam.Howlett@oracle.com, lorenzo.stoakes@oracle.com, mathieu.desnoyers@efficios.com, matthew.brost@intel.com, mhiramat@kernel.org, mhocko@suse.com, peterx@redhat.com, pfalcato@suse.de, rakie.kim@sk.com, raquini@redhat.com, rdunlap@infradead.org, richard.weiyang@gmail.com, rientjes@google.com, rostedt@goodmis.org, rppt@kernel.org, ryan.roberts@arm.com, shivankg@amd.com, sunnanyong@huawei.com, surenb@google.com, thomas.hellstrom@linux.intel.com, tiwai@suse.de, usamaarif642@gmail.com, vbabka@suse.cz, vishal.moola@gmail.com, wangkefeng.wang@huawei.com, will@kernel.org, willy@infradead.org, yang@os.amperecomputing.com, ying.huang@linux.alibaba.com, ziy@nvidia.com, zokeefe@google.com Subject: Re: [PATCH mm-unstable v4 5/5] mm/khugepaged: unify khugepaged and madv_collapse with collapse_single_pmd() Message-ID: References: <20260325114022.444081-1-npache@redhat.com> <20260325114022.444081-6-npache@redhat.com> <7760c811-e100-4d40-9217-0813c28314be@lucifer.local> <0223d45b-e8b4-49a7-882b-477250d0c14d@kernel.org> <26fcec86-ee78-4f5c-8ca5-0e6230699cfd@kernel.org> <20260331143538.f41a5fef4201a7384388f31c@linux-foundation.org> <1cdec848-4822-402d-91fb-50237488aec3@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1cdec848-4822-402d-91fb-50237488aec3@kernel.org> X-Rspamd-Queue-Id: A9236100002 X-Stat-Signature: unbd98xoog73odmetoahjtbr5tzgnn9n X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1775031453-233633 X-HE-Meta: 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 Nvs8avjQ ajOrYSTrr6UfNeEwAqgBc4xtoRDXQHKhcKae4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Apr 01, 2026 at 09:05:39AM +0200, David Hildenbrand (Arm) wrote: > On 3/31/26 23:49, Nico Pache wrote: > > On Tue, Mar 31, 2026 at 3:35 PM Andrew Morton wrote: > >> > >> On Tue, 31 Mar 2026 22:00:58 +0200 "David Hildenbrand (Arm)" wrote: > >> > >>> > >>> Right. > >>> > >>> The original code used > >>> > >>> bool mmap_locked = true; > >>> > >>> If the fix get squashed, maybe we should revert to that handling to > >>> minimize the churn? > >>> > >>> (this is not in stable, right?) > >> > >> "mm/khugepaged: unify khugepaged and madv_collapse with > >> collapse_single_pmd(): is presently in mm-stable. > >> > >> Doing a big rebase&rework isn't the done thing, I believe. So queue it > >> afterwards, add the Fixes: and tolerate the minor runtime bisection > >> hole. It ends up looking like a later hotfix. > >> > >> > >> Below is what I added to mm-unstable. I added a note-to-self to check > >> in on Nico's question at > >> https://lore.kernel.org/all/CAA1CXcCYLGQBy9nT-MSTPVK=XgWWtD6Af-QiA_6pXtM_2pybPg@mail.gmail.com/T/#u > >> > >> > >> From: "Lorenzo Stoakes (Oracle)" > >> Subject: mm/khugepaged: fix issue with tracking lock > >> Date: Tue, 31 Mar 2026 13:11:18 +0100 > >> > >> We are incorrectly treating lock_dropped to track both whether the lock is > >> currently held and whether or not the lock was ever dropped. > >> > >> Update this change to account for this. > >> > >> Link: https://lkml.kernel.org/r/7760c811-e100-4d40-9217-0813c28314be@lucifer.local > >> Fixes: 330f3758a3bc ("mm/khugepaged: unify khugepaged and madv_collapse with collapse_single_pmd()") > >> Signed-off-by: Lorenzo Stoakes (Oracle) > >> Reviewed-by: Lance Yang > >> Reviewed-by: Nico Pache > >> ... > >> Signed-off-by: Andrew Morton > >> --- > >> > >> mm/khugepaged.c | 12 ++++++++---- > >> 1 file changed, 8 insertions(+), 4 deletions(-) > >> > >> --- a/mm/khugepaged.c~mm-khugepaged-fix-issue-with-tracking-lock > >> +++ a/mm/khugepaged.c > >> @@ -2828,6 +2828,7 @@ int madvise_collapse(struct vm_area_stru > >> unsigned long hstart, hend, addr; > >> enum scan_result last_fail = SCAN_FAIL; > >> int thps = 0; > >> + bool mmap_unlocked = false; > >> > >> BUG_ON(vma->vm_start > start); > >> BUG_ON(vma->vm_end < end); > >> @@ -2850,10 +2851,11 @@ int madvise_collapse(struct vm_area_stru > >> for (addr = hstart; addr < hend; addr += HPAGE_PMD_SIZE) { > >> enum scan_result result = SCAN_FAIL; > >> > >> - if (*lock_dropped) { > >> + if (mmap_unlocked) { > >> cond_resched(); > >> mmap_read_lock(mm); > >> - *lock_dropped = false; > >> + mmap_unlocked = false; > >> + *lock_dropped = true; > >> result = hugepage_vma_revalidate(mm, addr, false, &vma, > >> cc); > >> if (result != SCAN_SUCCEED) { > >> @@ -2864,7 +2866,7 @@ int madvise_collapse(struct vm_area_stru > >> hend = min(hend, vma->vm_end & HPAGE_PMD_MASK); > >> } > >> > >> - result = collapse_single_pmd(addr, vma, lock_dropped, cc); > >> + result = collapse_single_pmd(addr, vma, &mmap_unlocked, cc); > >> > >> switch (result) { > >> case SCAN_SUCCEED: > >> @@ -2893,8 +2895,10 @@ int madvise_collapse(struct vm_area_stru > >> > >> out_maybelock: > >> /* Caller expects us to hold mmap_lock on return */ > >> - if (*lock_dropped) > >> + if (mmap_unlocked) { > >> + *lock_dropped = true; > > > > Hmm this was =false in David's example and = true here? Now i am also > > confused hahaha. It seems Lorenzo's code is correct. I think i > > responded to my own code changes, when I thought David was replying to > > Lorenzo's. > > I think I messed up that in my posting when manually applying :) > > So this here is correct. Yeah the fix-patch on top made it all confusing :) FWIW :P I also had claude do its thing to check it on this, and it gave the thumbs up. > > -- > Cheers, > > David Thanks, Lorenzo